The humoral and lymphocyte membrane receptor function of IgD is being studied in non-human primates. These studies include: 1) the ontogency of cells producing IgD and of cells with surface IgD; 2) the production of IgD antibody responses by animals immunized with various antigens, adjuvants and routes of immunization; 3) the binding of antigen by IgD-bearing lymphocytes from immunized animals; 4) the effects of anti-IgD on various in virto parameters of lymphocyte function; and 5) the relationship of the specificity of IgM and IgD on individual cells. Non-human primate models of autoimmune and infectious diseases will be utilized to study the involvement of IgD in disease processes.